Define evolution. How does it occur? Describe how fossils provide us evidence in support of evolution.

Hint: Evolution is a transition in the heritable features of biological populations over centuries. These traits are the expressions of genes that are transferred from parent to offspring during reproduction. Different traits tend to occur within a given population as a result of mutation, genetic recombination and other sources of genetic variation.

Complete Answer:
The slow process of modifying the heritage characteristics of organisms over millions of years leading to the creation of new species is known as evolution. According to Darwin's theory of evolution, natural selection is responsible for the creation of new organisms over time. The species that are better suited to live under the specified environmental conditions are selected by nature and reproduced.
Evolution occurs due to the following reasons
1. Accumulation of variations over generation
2. Natural Selection

- The variations that occur in these individuals are passed onto the next generation, while individuals with unfavourable variations die. But the precise cause of these differences is a mutation that contributes to speciation.
- Fossils are the remains of past species buried in sedimentary rocks.
- In different aged rock sediments, different fossils are formed. The analysis of fossils in various rock layers shows the time period that they lived. Thus, various forms of life have been created at different times in the history of the earth. Fossils demonstrate how evolution has contributed to the creation of complex life forms from simple ones through a gradual process.
- For example, the fossil bird Archaeopteryx is known to be a link between reptiles and birds suggesting that birds have evolved from reptiles. It indicates the presence of both birds and reptiles, such as the presence of teeth, wing feathers, clawed toes and tails.

Note: The study of fossils is called Palaeontology. It defines the age of fossils by using a carbon dating process. Evolution can be organic or Inorganic. The former deals with the changes happening in living organisms over time from the beginning of the life while the later deals with the changes in non living organisms.